There is known a single-phase three-wire output inverter as disclosed in Patent Document 1. This inverter includes three arms, and one of three-phase output terminals of inverter bridges is a neutral phase (O phase) of which a current command is constantly zero. In the inverter, current commands of the remaining two phases (U phase, W phase) other than the neutral phase (O phase) are sinusoidal current commands having a mutual phase difference of 180°. Thus, the inverter obtains single-phase three-wire PWM output voltage.
In the case of domestic wiring of the inverter, the O phase is subjected to ground connection to a pole transformer. When the inverter is activated, an output voltage of the inverter varies between a voltage between the O phase and the U phase and a voltage between the O phase and the W phase. This action is a variation of the entire potential of the inverter with respect to the ground potential of the O phase, which easily causes waveform distortion. In addition, the conventional inverter cannot deal with various types of loads such as a half-wave rectified load.
The present invention has been made in view of the above-described circumstances. An object of the present invention is to provide a single-phase three-wire power conversion device capable of dealing with various types of loads and suppressing waveform distortion.